Migrate PearlMCAbsorption to new api. Refs #7155

This has no unit test but is currently covered by the PEARL system test.
Formatting changes only: tabs->spaces. Refs #7156
Migrate OSIRISDiffractionReduction to new api. Refs #7156
Merge remote-tracking branch 'origin/feature/7155_migrate_PearlMCAbsorption'
Merge branch 'feature/7156_migrate_OSIRISDiffractionReduction'
Merge branch 'master' of https://github.com/mantidproject/mantid